A serogrouping system has been developed for gonococci which is based on a family of acidic polysaccharides designated Gc antigens which can be isolated from the phenol-water extract by DEAE chromatography. The objectives of this proposal are the extension and development of this serogrouping system. The system is to be applied to a large number of carefully defined gonococal strains to compare the relationship between Gc antigens and other gonococcal serotyping systems. In addition, correlations will be between serogroup type and clinical parameters such as disseminated disease, carrier state, antimicrobial sensitivity and reinfection. Studies are planned to investigate gonococcal strains which are non-groupable in the five known GC serogroups for new serogroup antigens. Methods are proposed for the improvement in the technique for Gc serogrouping to increase its specificity and sensitivity and to make the procedure more available for clinical application. Immunochemical and physicochemical studies on isolated Gc antigens are proposed in order that the nature of the antigenic determinants responsible for serogroup specificity might be defined. Finally, studies into the immunogenicity and potential immunoprotective value of these antigens is planned using plaque assay methods, bactericidal techniques and subcutaneous chambers in guinea pigs.